Atherosclerotic vascular disease remains one of the most common causes of death in the United States. The broad goal of the proposed studies is to generate a better understanding of the mechanisms of this disease process. Atherosclerosis is an inflammatory disease. It is mediated in part by monocytes that are recruited into the vessel wall by adhesion molecules, including E- and P-selectin. Two 1(1,3)-fucosyltransferases, FucT-IV and FucT-VII, participate in the synthesis of active E- and P- selectin ligands on leukocytes. Thus, expression of these fucosyltransferases, and therefore selectin ligand activity, may regulate monocyte trafficking into the vessel wall and development of atherosclerosis. The experimental goal of this proposal is to test the hypothesis that monocyte-specific FucT-dependent selectin ligand activity modulates the development of atherosclerosis. FucT- dependent changes in atherosclerotic lesion pathology will be assessed in the low density lipoprotein receptor (LDL-R)-deficient mouse model of atherosclerosis. FucT activity in LDL-R(-/-) mice will be deleted globally and in a monocyte specific manner using gene targeting strategies, as well as reconstituted in a monocyte-specific manner using transgenesis. FucT-dependent changes in atherosclerosis in vivo will be correlated with FucT-dependent monocyte selectin ligand activity measured in a flow chamber in vitro. The specific aims of this proposal are to: 1) Quantify atherosclerotic lesion size, and determine the qualitative alterations of the lesion in LDL-R(-/-) mice in which FucT-IV, or FucT-VII, or both FucT-IV and FucT-VII are deleted. 2) Determine the cellular adhesion parameters that enable FucT-IV- and/or FucT-VII-dependent monocyte tethering and rolling on E- or P-selectin under shear. 3) Define the selectin ligand-dependent monocyte/macrophage- specific contribution to atherogenesis by quantifying lesion size and determining the qualitative alterations of the lesion in LDL-R(-/-) mice with (a) monocyte-specific deletion of selectin ligand activity, and in (b) mice in which monocyte-specific expression of selectin ligand activity has been reconstituted by transgenesis. Together, the proposed experiments will determine the functional role of FucT-IV and/or FucT-VII in generating the selectin ligand activity necessary for atherogenesis. The experiments will also determine the quantitative and qualitative monocyte-specific selectin-dependent contributions to atherogenesis. This knowledge will contribute to the development of improved or novel preventive strategies, diagnostic procedures, and therapeutic options for atherosclerosis, which will ultimately reduce the morbidity and mortality associated with the disease and its sequelae.